HAL-IRD
Not a member yet
83947 research outputs found
Sort by
Born to be alive. Isotopic evidence of investment in the survival of immature individuals in the Neolithic period, ecological influences and the construction of social identities
No full textInternational audienc
Nonphotochemical quenching and beyond: multi-layered photoprotection shapes light-stress tolerance across seasonal niches in Arctic diatoms
No full textInternational audienceThroughout their species seasonal succession, diatoms of the Arctic Ocean experience a radical habitat transformation, from surviving the dimly lit winter within sea-ice or in the water column, to rapid growth under increasing irradiances, forming massive spring blooms beneath melting ice and later in open waters. Therefore, their evolutionary path has been moulded by the opposing challenges of maximizing light capture part of the year while maintaining highly efficient photoprotection capacities to limit photodamage upon bursts of supra-optimal illumination. Two main photoprotection mechanisms exist in diatoms i) nonphotochemical quenching (NPQ) supported primarily by the xanthophyll cycle (XC) and stress-related Lhcx antenna proteins and, ii) a rapid repair cycle of photosystem (PS) II core protein, PsbA, upon photodamage. Previous studies suggest that freezing temperatures slow protein turnover and favour photoprotection strategies that rely primarily upon XC-NPQ in polar taxa. We aim to revisit this hypothesis by dissecting the high-light response of five Arctic diatom species that dominate contrasting ecological niches: sea-ice, marginal ice-zone and open waters. We exposed each species to a high-light stress and subsequent recovery period under low light, with and without, inhibitors of XC-NPQ (dithiothreitol) or of plastid protein translation (lincomycin), blocking de novo replacement of PsbA. We confirmed the crucial role of XC-NPQ in protecting PSII but also report unexpected observations that challenge our current understanding of psychrophile species response to light stress. First, the impact of lincomycin on PSII photoinhibition was stronger than that of DTT, despite PsbA turnover being undetectable by immunoblots in most cases. Second, while our data support planktonic species showing better tolerance to high light than sympagic species, we found unsuspected diversity in photoprotection strategies. We hypothesize that these differences support a gradient from conservative strategies, possibly optimized for survival in the extreme sea-ice habitat of sympagic species, to productivity-oriented strategies in open water planktonic species dominating during the bloom period. In the transforming, brighter, Arctic Ocean, the adaptedness of this community-wide strategy scheme could be undermined, shaking up the historical dominance of certain diatom taxa
African zoonotic schistosomiasis: a paradigm shift
No full textInternational audienceIn Asia, Schistosoma japonicum infects humans and many animal species, making it a zoonotic disease. In Africa, the two major species infecting humans are Schistosoma mansoni and Schistosoma haematobium, which cause mesenteric and urogenital schistosomiasis, respectively. Despite the significance of these parasitic infections for human health, few studies have examined the zoonotic aspects of these parasites. In the initial section of this article, we examine the advancements made in analysing the zoonotic characteristics of S. japonicum, with a particular emphasis on the diverse scenarios observed in the field. We also review the role of rodents and non-human primates in transmitting S. mansoni and the emerging importance of cattle and rodents in hybrid schistosomiasis involving S. haematobium and Schistosoma bovis (a livestock and rodent parasite). Second, we examine the genetic diversity of these hybrid forms across their distribution in West Africa. Hybrid forms exhibit considerable diversity across all spatial levels, ranging from the transmission site to the national scale. Ultimately, we aim to explore the implications of zoonotic urogenital schistosomiasis in relation to the role of each host in its transmission, together with parasite gene flow, parasite diversity and parasite virulence. This article is part of the Royal Society Science+ meeting issue ‘Parasite evolution and impact in action: exploring the importance and control of hybrid schistosomes in Africa and beyond’
Geodynamo Simulation Explorer: a filterable and visualisable catalogue to explore geodynamo simulations
No full textWe present a new web tool, Geodynamo Simulation Explorer, to survey available published simulations of rapidly rotating spherical dynamos.With numerical codes and computers being increasingly efficient, recent years have seen a surge in the number of publications presenting such computations.Our tool comes as an interactive catalogue that allows exploring existing dynamos with respect to input and output dimensionless parameters, choosing from various dynamo setups (e.g. choice of boundary conditions, couplings at play, etc.), with the possibility to test scaling laws on a filtered set of simulations. It also links each dynamo to its associated publication and possibly to online datasets.Thought of as a collaborative and scalable initiative, the web interface allows uploading new simulation metadata.The whole interface, displayed as a website, is designed for the community to have a better overview while driving transparency, open-source initiatives, and FAIR principles (Findable, Accessible, Interoperable, Reusable).Check it out and feed it at https://geodyn.univ-grenoble-alpes.fr/explorer/
Rapport sur les services climatiques réussis dans le monde et leurs critères de succès: Livrable commun au Projet ciblé TRACCS-PC1-DIALOG (D5.3) et au Projet Ciblé TRACCS-PC3-DEMOCLIMA (D1)
No full textLes enjeux socio-économiques liés aux effets du réchauffement climatique sont tels qu’une demande croissante d’informations climatiques adaptées pour la mise en place de stratégies d’atténuation et/ou d’adaptation est clairement exprimée par les secteurs économiques (e.g. agriculture, énergie, tourisme, infrastructures terrestres ou maritimes, etc…) et par les territoires/régions qui mesurent pleinement leursvulnérabilités. En réponse à ces demandes, de nombreux projets de recherche nationaux (e.g., la "Convention relative à l’attribution d’un appui financier au bénéfice des services climatiques", signée entre le Ministère de la Transition Écologique et Solidaire (MTES) et le CNRS en mars 2017, ou le développement du portail DRIAS), européens (e.g., le programme ERA4CS « European Research Area for Climate Services » du JPI Climate, ou encore Copernicus) ou internationaux (e.g., les outils développés par la NASA, le GIEC…) ont permis le financement de « services climatiques ». Plusieurs acteurs opérationnels nationaux et européens développent et mettent à disposition des « services climatiques » via des plateformes souvent libres d’accès et enfin, apparaissent sur le marché des bureaux d’études dont l’activité commerciale vise le développement de « services climatiques » à la carte et adaptés aux demandes des clients.L’offre pour les « services climatiques » est donc aujourd’hui multiforme par l’information fournie (données climatiques « simples », indicateurs, outils d’aide à la décision) et par son mode de développement. Face à cette diversité, les enjeux sont de documenter et comprendre le paysage des services climatiques actuels, de faire ressortir les besoins, et de se munir de moyens pour caractériser la réussite des services climatiques, pour évaluer l'existant et guider le développement de nouveaux projets. Menée conjointement par les projets ciblés DIALOG (PC1) et DEMOCLIMA (PC3) du PEPR TRACCS, cette étude vise quatre objectifs :i) Documenter le paysage actuel des services climatiques (section 2) en France et dans le monde (identifiés par la communauté TRACCS) en les présentant par usages et cibles ;ii) Identifier des besoins non satisfaits vis-à-vis des services climatiques (section 4) ;iii) Identifier un ensemble de critères de réussite d'un service climatique pour les évaluer (section 5) ;iv) Proposer des bonnes pratiques pour atteindre ces critères de réussite (section 6); ces éléments guideront les choix des futurs démonstrateurs qui seront conçus et développés au sein de DEMOCLIMA.Notre travail repose en grande partie sur le recueil de dires d'acteurs des "services climatiques", dans une approche "bottom-up"
On the tropical nature of an intense Mediterranean cyclone in the ocean-atmosphere system
No full textInternational audienceThe Mediterranean basin hosts a large number of cyclones every year. Among them, some rare cases named medicanes present similarities with tropical cyclones but their dynamical characteristics are debated. The ocean-atmosphere dynamics of Medicane Ianos (2020) are studied here through km-scale fully coupled ocean-wave-atmosphere simulations. These allow investigating the tropical nature of Ianos in terms of both atmospheric circulation and thermal structure, and of oceanic cold wake response which feedbacks negatively onto the cyclone's intensity. Simulations match in situ and remotely sensed observations in the ocean and atmosphere well. Three life cycle phases can be distinguished with a mature phase during which the cyclone is compact and axisymmetric. Orographic acceleration is shown to induce asymmetry in the cyclonic winds and precipitation prior to landfall. These are expected to be common for medicanes given the small scale and steep orography of the Mediterranean basin. Ianos distinguishes itself from previous medicanes by its intense cold wake wherein the sea surface cooling exceeds 3\textdegree{C}. The wake results mainly from mixing at the base of the mixed layer, while surface fluxes play a secondary role as revealed by temperature budget analysis. The amplitude and dynamics of the wake are alike those found in tropical cyclones of category 2 or more. A deep warm core cyclonic eddy on Ianos' track is responsible for an interruption in the cold wake which coincides with the re-intensification of the cyclone during its mature phase. Such eddies are widespread in the Mediterranean but poorly constrained in models
Artificial selection of suppressive or conducive rhizosphere microbiota circumvents the growth-defense trade-off due to a foliar pathogen
No full textInternational audiencePlant-pathogen interactions are influenced by physiological responses and rhizospheric microorganisms, which can create disease-suppressive or disease-conducive soils affecting pathogen dynamics. This study used artificial selection to shape soil microbiota conditioned by Arabidopsis thaliana to either suppress or promote the foliar pathogen Pseudomonas syringae DC3000 (Pst). Over successive iterations, plants were inoculated with Pst, and soils were selected based on plant symptoms: enhanced resistance (suppressive), increased susceptibility (conducive), or no selection (control). A non-inoculated group (non-conditioned) was also included. Disease symptoms, Pst proliferation, and rhizosphere microbiota were monitored each iteration. Selection for suppressive soils reduced disease severity and Pst levels, while conducive soils showed the opposite. Each soil type was enriched in distinct bacterial communities. A growth-defense trade-off was evident in control soils but less so in selected soils. Gene expression analysis revealed that plant hormone homeostasis, especially salicylic acid (SA) and jasmonic acid (JA) played key roles with SA linked to local defense and JA to systemic responses. This work highlights artificial selection as a promising strategy to modulate soil microbiota, influencing plant-pathogen interactions and microbial dynamics
Large-scale genome-wide association study of 398,238 women unveils seven novel loci associated with high-grade serous epithelial ovarian cancer risk
No full textInternational audienceABSTRACT Background Nineteen genomic regions have been associated with high-grade serous ovarian cancer (HGSOC). We used data from the Ovarian Cancer Association Consortium (OCAC), Consortium of Investigators of Modifiers of BRCA1 / BRCA2 (CIMBA), UK Biobank (UKBB), and FinnGen to identify novel HGSOC susceptibility loci and develop polygenic scores (PGS). Methods We analyzed >22 million variants for 398,238 women. Associations were assessed separately by consortium and meta-analysed. OCAC and CIMBA data were used to develop PGS which were trained on FinnGen data and validated in UKBB and BioBank Japan Results Eight novel variants were associated with HGSOC risk. An interesting discovery biologically was finding that TP53 3’-UTR SNP rs78378222 was associated with HGSOC (per T allele relative risk (RR)=1.44, 95%CI:1.28-1.62, P=1.76×10 -9 ). The optimal PGS included 64,518 variants and was associated with an odds ratio of 1.46 (95%CI:1.37-1.54) per standard deviation in the UKBB validation (AUROC curve=0.61, 95%CI:0.59-0.62). Conclusions This study represents the largest GWAS for HGSOC to date. The results highlight that improvements in imputation reference panels and increased sample sizes can identify HGSOC associated variants that previously went undetected, resulting in improved PGS. The use of updated PGS in cancer risk prediction algorithms will then improve personalized risk prediction for HGSOC
Uncovering hidden sensitivity: Inter-individual growth variation in earthworms under fungicide exposure
No full textInternational audienceEnvironmental risk assessments (ERAs) of chemicals typically rely on standardized ecotoxicological tests that overlook inter-individual variability, despite its importance in ecological resilience and evolutionary success. Contaminants can disrupt individual differences by altering life-history traits, amplifying fitness disparities, favoring certain phenotypes, and reducing genetic diversity, ultimately impacting population dynamics and adaptability. However, the extent to which pollutants influence inter-individual variability and its population-level consequences remains poorly understood. To address this, our study examines the inter-individual variability of growth trajectories in the earthworm Aporrectodea caliginosa in response to sublethal exposure to the two active substances of Swing® Gold fungicide. Using a longitudinal design with 30 exposed and 30 unexposed individuals, we compared mean and inter-individual growth rate variability. While the fungicide had a weak effect on the cohort’s mean growth rate, we observed a three-fold increase in inter-individual variability in the exposed group. This increase highlighted a subset of highly sensitive individuals, whose growth was reduced by up to 10% compared to the average response. Our results suggest that focusing solely on population mean effects could overlook impacts on sensitive individuals, who could serve as early indicators of environmental stress. Incorporating individual variability into ecotoxicological studies is challenging due to the labor-intensive nature of individual monitoring and the need for larger datasets. Nonetheless, these efforts are essential for refining higher-tier ERA frameworks, improving safety factors for intraspecies variability, and defining regulatory thresholds. A better understanding of how contaminants affect inter-individual variation will enhance the accuracy and ecological relevance of risk assessments, ultimately capturing the long-term implications for population and ecosystem dynamics
Domoic acid production by a Pseudo-nitzschia australis strain under zinc and copper exposure
No full textInternational audienceThe diatom species Pseudo-nitzschia australis can produce domoic acid (DA), a neurotoxin- responsible for amnesic shellfish poisoning. Copper (Cu) and zinc (Zn) are essential trace metals for marine phytoplankton, but they can become either limiting or toxic at pico- to subnanomolar ionic concentrations—levels that are can be reached in coastal ecosystems. The effect of exposure to these metals on DA production remains unclear for Cu and is largely unknown for Zn. In this study, we investigated the effects of toxic picomolar concentrations of Cu²⁺ and four non-limiting concentrations of Zn²⁺ on the metabolism and physiology of a toxic P. australis strain isolated from the coastal waters of North Biscay (France). Using principal component analysis, we observed changes in cell populations over time depending on metal exposure. Cu²⁺ toxicity was marked by a 35 % decrease in maximum cell density and a reduction in growth rate (µ₊Cu = 0.55 µₐₓ). DA production was differentially modulated by the two metals: toxic Cu²⁺ levels stimulated DA synthesis (+200 %), while elevated Zn²⁺ bioavailability significantly decreased it (by up to –85 %), including when Zn²⁺ was combined with toxic levels of Cu²⁺ (–65 %). We further discuss DA production by P. australis as a potential protective mechanism against oxidative stress. Additional data on intracellular glutathione (GSH) quotas—an important reactive oxygen species (ROS) scavenger and Cu²⁺ chelator— are presented and linked to Zn2+ bioavailability. GSH cell quotas were significantly correlated with DA production (p < 0.05) further supporting existing links between metal exposition, oxydative stress and DA production. This study suggests that ambient concentrations of Cu²⁺ and Zn²⁺ are critical factors regulating DA production in coastal marine systems